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Physics professor Dan Dahlberg throws his weight around--actually, several 30-pound weights--to show how forces work in a performance by the Physics Force in Northrop Auditorium.

Falling for physics

It's a wonder Physics Force team members are in one piece, given the lengths they go to to open up the world of physics

By Deane Morrison

Jan. 10, 2006

Dangling in a harness 20 feet above the Northrop Auditorium stage on the Twin Cities campus, Aaron Pinski watches as his good friend Dan Dahlberg aims a cannon squarely at him. Beyond the footlights a large audience waits, knowing that at the count of three Dahlberg will shoot a ball from the cannon and Pinski will be unceremoniously dropped. The question is, will Pinski avoid the projectile by falling?

So begins the most spectacular demonstration by the Physics Force, a group of wild and crazy physicists who use highly visual and entertaining stunts to teach the elements of their science. You can catch their annual free, hour long public show at Northrop Auditorium at 7 p.m. this Thursday, or, if you're on campus, any morning this week. (Warning: the morning shows will be packed with schoolkids.) Besides Dahlberg, a University professor of physics, and Pinski, who teaches at Kennedy High School in Bloomington, the troupe includes five other current or retired area physics teachers. Their shows are probably the only place you'll see grown men shooting a roll of toilet paper 30 feet into the air, collapsing a 55-gallon drum, or propelling themselves on a cart by emptying a fire extinguisher. Also, in a reversal of what happens at some theatrical events, a Physics Force show features the performers throwing eggs. In their case, they catch the eggs on either a hard surface (you know what happens) or in a sheet, to demonstrate that lengthening the time a force is applied can minimize its effects. It's the principle at work when a car airbag stops a human body.

"We want to show that physics is fun and interesting, and that it's something people can understand," says Dahlberg. "People will come and be entertained, but they'll be surprised at how much they learn."

When the Force swings into action, it's hard to say whether the physicists or the audience has more fun.

"We want to show that physics is fun and interesting, and that it's something people can understand," says Dahlberg. "People will come and be entertained, but they'll be surprised at how much they learn."

The Force got its start 20 years ago, thanks to the efforts of the late Philip Johnson, who designed and constructed science demonstrations for classes at the University. A specialist in large-scale physics demonstrations, he produced a physics "Road Show" that was used in high schools, elementary schools, and colleges. After Johnson died in 1995, the group carried on his legacy. Over the years they've wowed crowds at Epcot Center, the "Newton's Apple" public television show, the German television show "Knoff-Hoff" (an approximation of the German pronunciation of "know-how"), and the Minnesota State Fair, not to mention innumerable school venues around the state. In 2003, the University recognized Dahlberg with an Outstanding Community Service award for his contributions to public education.

The troupers realize that not everyone who watches them perform will be inspired to embrace physics as a career. But thousands of screaming, oohing and aahing elementary kids are proof that physics need not amuse only the Einsteins and Curies among us.

"Phil Johnson used to say, 'You don't have to be a concert pianist to enjoy a symphony, and you don't have to be a physicist to enjoy physics,'" says Dahlberg.

OK. The time has come. Dahlberg has aimed his cannon, Pinski is tired of hanging in midair, and we're going to find out if the ball will hit him. The answer is suggested by the large baseball mitt Pinski is holding up. Dahlberg counts to three and shoots the ball at the same instant trouper Jon Barber releases Pinski's support rope. Sure enough, the ball and Pinski both obey the law of gravity, and Pinski catches the ball a split second before hitting a cushion on the stage floor.

If you can't make the public show Thursday night, the remaining morning shows are at 10:20 a.m. Wednesday and Thursday and 10:10 a.m Friday.